Can. 1513 §1. The joinder of the issue (contestatio
litis) occurs when the terms of the controversy, derived from the petitions
and responses of the parties, are defined through a decree of the judge.

§2. The petitions and responses of the parties,
besides those in the libellus which introduces the litigation, can be expressed
either in a response to the citation or in the oral declarations made before
the judge; in more difficult cases, however, the judge must convene the parties
to resolve the doubt or doubts which must be answered in the sentence.

§3. The decree of the judge must be communicated to
the parties; unless they have already agreed to the terms, the parties can make
recourse to the judge within ten days in order to change them; a decree of the
judge, however, must resolve the question as promptly as possible (expeditissime).

Can. 1514 Once established, the terms of the
controversy cannot be changed validly except by a new decree, for a grave
cause, at the request of a party, and after the other parties have been heard
and their arguments considered.

Can. 1515 After the issue has been joined, the
possessor of the property of another ceases to be in good faith; therefore, if
the possessor is sentenced to restore the property, the person must also return
the profits made from the day of the joinder and repair any damages.

Can. 1516 After the issue has been joined, the
judge is to prescribe a suitable time for the parties to present and complete
the proofs.